Quote:
Originally Posted by hcl123
i had a VW Golf II 1.9TDI rated 115HP and with a change of turbo (NO NOT that much turbo pressure) and control box tweaks and an adapted Passat gear box transmission( more robust).. and i had a 270HP motor at the dynamometer...
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I don't know where you live, but VW never produced a Golf II with a 1.9 TDI engine. The GTD had a 1.6 turbo diesel engine with 70-80 hp.
Quote:
Originally Posted by hcl123
Petrol doesn't allow high rates of compression due to physical and chemical proprieties of the substance... and because of that, including those physical and chemical proprieties, is a "slow burner" compared with Diesel that literally explodes inside the cylinders under high compression. Experimental engines have achieved rates of 40:1 in volume compression  |
It might surprise you but the Peugeot 908 HDI engine has a compression ratio of only 14:1 (see
here). That is not a lot more than modern direct injected petrol engines. For instance, the Ferrari 458 has a CR of 12.5:1.
Quote:
Originally Posted by hcl123
Max power is illusory  Power = troque(force) x speed of the engine. Power "on the ground" by every unit of time in the average of the length to be measured is the key. An engine to achive 10K RPM has to pass from 3/4K RPM all up to 10K RPM... by the time those obsolete petrol engines achieve its max power superior to diesels they have already lost half mulsane straight, because their torque is so much inferior!... |
Clearly you did not read the link I posted earlier in this thread:
http://www.physicsforums.com/showthr...53#post1231053 Peak power and a wide power band are important for acceleration, peak torque isn't.
Because you have been a Golf owner, perhaps the previous Golf GT is a good example. VW made the car with a diesel and a petrol engine:
- petrol: 1.4 TSI (supercharger + turbo), 125 kW @ 6000 rpm, 240 Nm @ 1750 rpm, 1268 kg
- diesel: 2.0 TDI, 125 kW @ 4200 rpm, 350 Nm @ 1750 rpm, 1303 kg
Guess which car is faster. These are the performance numbers for the DSG gearbox:
- petrol: 0-100 km/h in 7.7 sec, top 218 km/h
- diesel: 0-100 km/h in 8.2 sec, top 218 km/h
Both cars have the same top speed because they have the same power. The petrol car accelerates faster because of its lower weight. The higher torque of the diesel can not compensate for this weight disadvantage.
Finally, the fuel consumption numbers, again for DSG gearbox:
- petrol: 7.3 liter/100 km
- diesel: 6.4 liter/100 km
Yes, the diesel car has better fuel economy. However, if you take into account that diesel has a 10% higher energy density (see
here), the difference is not so big.
Quote:
Originally Posted by hcl123
... is it that diesels CAN rev high to ??... not has much as petrols because its explosive nature of combustion make them harder to achieve the proper mechanical balance of its moving parts ?? ... yet achieve close to 20% superior fuel consumption efficiency with an equal or superior overall efficiency ??
So don't get surprised if those 3.7L diesels achieve 8K RPM and the times per lap in 2011 are very close to the times of 2010...
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A diesel engine revving to 8000 rpm
How high must the cetane number be to achieve such high rpm? Race diesel engines don't produce power by revving, but by injecting more fuel (= more torque).